Depolarized primary cell



Jan. 30, 1962 R. D. BLUE ETAL 3,019,279

DEPOLARIZED PRIMARY CELL Filed March 20, 1958 ATTORNEY United States The irivelition is directed toward the production of electricity by means of a primary c'ell `i.e., one which converts chemical energy into electrical energy. More especially itis directed toward such cell having an anode of a metal electropositive to carbon, e.`g., magnesium, magnesium base-alloy, zinc or zinc-base alloy, and a cathode of porous carbon through which an aqueous electrolyte is passed containing depoiarizing materials.l

Cells for `theproduction of electricity having 'two electrodes, one with Aa high positive or oxidizing potential, the anode, 'and one with a Stroirg negative or reducing potential, the cathode, 'have long been known. The material most 4commonly employed `as the anode is zinc, and that most commonly employed as the cathode lis carbon, graphite, copper, or platinum.

The surface ofthe anode, e.`g., zinc, oxidizes, ie., undergoes a positive increase in valence (goes from Zero to a higher value). As a `result thereof, zinc atoms are converted `to `in'c `ions' which enter the electrolyte 4according tothe equation:

Zn;-' Zn`l-2e As a result thereof, the anode is dissolved away. The electrons produced by the above reaction travel by way of an external circuit to the `cathode and at the interface between the cathode and electrolyte react with the hydrogen ions which are drawn thereto through the electrolyte as a result of the lower positive potential thus set up. The reaction at the submerged surface of the cathode or at the interface between the cathode and the electrolyte is regarded essentially as a reduction of the hydrogen ions or of ions containing a hydrogen Component such as Olla or OEI toatomic and/or molecular hydrogen.

-If a primary cell is to continue to provide useful electrical potential beyond a brief period of operation, the reactions mentioned above must be reversible to .some eirtent. Unless there is such reversibility, van overvoltage develops `which is a back electroinotive force, ie., a potential Vin the reverse 'direction to that initially present `in the electrolytic system. Overvoltage is due to 4a condition develpingin a cell which is referred to generally as polarization.

Polarizatii may be considered to be due either t depletion of the substances necessary for the occurring electrolytic process at a faster rate than they are being supplied or to the accumulation of the products ofthe electrolytic process at a rate faster than they are being removed'. APolarization in its 'effect is -similar to an ohmic resista-nce forming part of -a circuit and is a condition which must-be avoided or overcome to a large eitent in primary cells, Among the proposed methods of overcoming the effects `of polarization, known as `depolarization, `are -mechnicaljagitation of the electrolyte, adjust ment of current and voltage conditions, e.g., superimposing alternating current or intermittently attaching the electrodes to an outside electrical sourceto `cause current to lllow through the cell in the opposite direction, and ernployment of depolarizing agents known generally as depolarizers. V, p

Depolarizers are usually `classilied as either oxidizing or atent 2 reducing depolarizers. oxidizing vdepolarizers 'are 'introf duced at the cathode. Among oxidizing "depolarize'rs are chlorine and oxygen which react with the hydrogen values tending to accumulate Vat lthe cathode. Reducing de polarizers are introduced at the anode. Among reducing depolarizers are acetylene and inorganic compounds yielding the lower of polyvalent cations such as ferrous, chromous, and vanadous ions. 4 p l' 'For uses of electricity in areas not accessible to 'dynaf mo-produced electrical energy and which 'do not lend themselves to utilizing energy produced by gasoline or diesel-powered generators, there is a need for a primary electric cell. For a limited number of such uses the Leclanche cell has met this need. However, the electroly'te-depolarizer composition of the Lechanche cell renders the ratio of its weight and volume to lthe power and energy producible"therefromtoo high for use in com? pact and mobile cells. The lmethods heretoforeproposed for overcoming the effects of polarization have notjadequately overcome such effects and have not lent themselves to depolarizing compact and Vmobile primary cells having a relatively low ratio 'of cell Weight to lthe kiloi watts and kilowatt hours which the cell is capable of 'pro ducing. There is, consequently, a need for more effective methods of depolarization, and for methods more adapt'- able for use in compact low-weight and mobile primary cells and for an improved primary cell containing such depolarizing means.

Therefore, the objects of the invention are to provide such method and improved cell.

A means by which depolarization is attained in aprirnary cell and a method employing such c'ell according to the invention will be made clear by the following description and the annexed drawing and are concisely defined by the appended claims. i

The invention is an improved primary cell and method employing such cell for the production of electrical current consisting essentially of passing an aqueousV electrolyte containing an alkali or alkaline earth bromide Vin solution, into which chlorine gas is admiXed, through` a porous carbon cathode and thence into Contact with an anode of magnesium, magnesium-base alloy, zinc, or zincbase alloy. y.

FIGURE 1 of the drawing is a schematic view of a sectional side elevation of the cell of the invention with the electrodes in a vertical position. FIGURE 2 is, a horizontal section taken along line 2-2 of FIGURE l. Y

FIGURE 3 is a schematic side elevational view of a battery or multiple-cell unit of the invention.

Referring to the drawing in more detail, and particularly to FGURES l and 2, there is shown graphite slab 10, porous carbon plate 12, and magnesium-ba'sealloy plate 14 in substantially `vertical position held iirmlytegether by electrically insulating clamps 1,5. Graphite slab 10 has inwardly extending projection 16, which together with graphite slab 10 and carbon plate 12, deiine narrow distributing chamber 20. Graphite slab 10 is: substantially impervious to the passage of iluids whereas carbon plate VA12 readily permits the passage ofy Huids therethrough. The opposite faces of plates 12 and 14, which are elose together, deiine electrolytic chamber 22 and are the cathode and anode, respectively, of the electrolytic chamber. The distance between the opposing faces of slab 10 and plate 12 are on the order of 0,1 to 0.25 inch. The distance between the opposing `faces of cathode 12 and anode 14 can be from 0.05 to 05 inch or more but -usually does Anot eicceed 0.125 inch in a new cell since close spacing of ano-de and cathode is preferable to minimize the `internal resistance of the cell. l w l I In an opening in the top of projection 16 `of slab 10 is tapped recess 24 in which feed line 26 is threadedly engaged. Feed line 26 admits electrolyte from a source not shown to distributing chamber under sufficient pressure to force the electrolyte through cathode 12 into chamber 22 and maintain chamber 22 completely filled during operation.

- Electrically insulating gasket 28 forms a continuous seal all around the cell between projection 16 and anode 14 near the outer edges of the surfaces thereof which face each other and thereby entirely incloses chamber 22 except for tapped opening 30 in the gasket top, into which gas outlet line 32 (primarily for H2 produced) is screwed, and tapped opening 34 in the bottom, into which electrolyte outlet line 36 is screwed. Gasket 28 is of any suitable resilient nonconducting'inert material, eg., Saran, a copolymer of vinyl chloride and vinylidene chloride. Outlet line 36 conducts electrolyte from the cell back to a chlorinating means, not shown, where chlorine gas is admixed with the electrolyte. Connected to line 36 is pipe 38, having valve 40 therein, to provide a means for bleeding oif electrolyte from line 36 as desired.

Terminal 42 on cathode .12 and terminal 44 on anode 14, to which are attached lead lines 45 and 4S respectively, provide an external circuit for conducting the current produced by the cell to a work load represented by incandescent lamp 47, thereby providing a means for utilizing the electrical energy capable of being produced by the cell.

Referring to FIGURE 3 of the drawing there is shown a multiple cell unit formed of a number of, cells represented by A, B, X and Y of the type illustrated in FIG- URES l and 2 abutting one another so that slab 10 of one cell is fayed with metal anode 14 of the adjacent cell. j

-Conducting graphite cement 49 is used to form good electrical contact between the abutting electrodes. The so-positioned cells are rmly clamped together as by means of electrically insulating clamps 50. The cells are thereby electrically connected in series. Line 52 supplies electrolyte to feed lines 26a, each of which then carries the electrolyte to the distributing chamber of each of the cells as in the single cell of FIGURE 1. Gas outlet lines 32a lead from each of the cells into common line 58 which carries away the hydrogen or other gases produced. Electrolyte outlet lines 36a, each leading from the electrolytic chamber of a cell, empty into common discharge line 62. Line 34a, having valve 40a therein, serves as a means for bleeding eletcrolyte from line 62. Although slab 10 is shown of graphite, it may be of any rigid material so long as electrical contact is provided to cathode 12. The anode is preferably a magnesium-base alloy consisting of between 2 and 8 percent Al, 0.5 to 4 percent Zn, 0.1 to 0.4 percent Mn, and the balance Mg, but it may be vMg or Mg-base alloy containing at least 85 percent lMg or any Zn-base alloy or commercial grade Zinc employed in the manufacture of zinc electrodes. The cell can be made 4to operate in any position between vertical and near horizontal, but it is preferred that it be substantially vertical.

In practicing the invention employing a cell of the type illustrated in FIGURE l, a soluble bromide, such as a bromide of an alkali or alkaline earth metal, is dissolved in water or in an aqueous solution, e.g., ocean brine, to provide the electrolyte of the invention. Bromine may be employed in the electrolyte, instead of the bromide, in the presence ofthe suggested metallic ions. The concentration of the bromine component in the electrolyte should be at least about 8 grams/liter; it is preferred that it be between 16 and 24 grams/liter. Chlorine gas is pumped into the bromide-containing electrolyte. The pH of the electrolyte is preferably maintained below a value of 3. The chlorine gas is conveniently introduced by merely admitting it from a convenient pressurized container into the electrolyte line 26 preferably just before the electro- 'lyte reaches the circulating pump (not shown). The chlorine is admitted in an amount sufficient to maintain a total oxidizing normality in the-electrolyte of `at least 0.1

N and preferably 0.6 N. It is thought that the dissolved chlorine gas replaces the bromine ions in the electrolyte to form chlorine ions and a species of bromine which is thought to comprise one or more of: dissolved liquid and/or gaseous bromine and reaction products between bromine and water such asl oxygenated bromides, e.g. hypobromite or bromate.

The electrolyte containing the chloride and the dissolved bromine species is circulated through the cell, as by a pump, not shown, the electrolyte entering through line 26 into distributing chamber 20 and thence being forced through the pores of cathode 12 into electrolytic ch-amber 22 and therefrom to outlet line 36. It is preferable that a lter be employed in the feed line to remove suspended matter.

Hydrogen which is produced' in the cell tends to accumulate at the cathode according to the reactions In the absence of a depolarizing agent, the thus-accumulating hydrogen would polarize the cathode. However, the dissolved bromine species, serving as the etective depolarizing agent, reacts with an appreciable percentage of the hydrogen. The reactions thought to take place at the cathode are l H2+Br2 2+213 l The hydrogen is removed from the cathode surface both by the above oxidation reaction and by the motion of .the electrolyte in the direction of the anode.

At the anode the principal reaction is There are, however, secondary or parasitic reactions at the anode due to the presence of the hydrogen ions and a species of bromine whether it be in the ionic, atomic or molecular bromine form. v These secondary reactions4 are thought to be:

An appreciable amount of hydrogen is thereby also removed from the interface between the electrolyte and the anode and/or from the surface of the anode. The cell is thereby also depolarized at the anode as well as the cathode by the presence of the bromine species according to the invention. The electrolyte, passing out throught outlet 36, therefore, contains both MgBr2 and MgCl2 which are carried back to the chlorine gas-mixing means (not shown) where the electrolyte is brought in contact with additional chlorine gas; there the following reaction takes place:

As the cell continues to operate, the percentage of magnesium chloride continues to build up. It has been found advisable to limit the percentage of the magnesium chloride to about 15 percent or a limit of 3.8 percent of the Mg component because percentages in excess of that amount tend to react to produce some magnesium oxychloride which adheres to'some extent to the magnesium anode forming an electrically resistant layer which interferes with the current ow. The pH is maintained below a value of 3 by addition tothe' electrolyte of an inorganic acid, e.g., aqueous HC1 or- H2804, which forms substan-l tially no precipitate. When thepl-I value rises above 3', oxychloride flo'cculant tends to form and'lo'dge in the pores of the carbon cathode'.4 5' -v -l To maintain the Mg ion content as desired some brine is bled ott throughpipe 3S by opening valve`-40,l and Vfrom that employing one cell.

fresh brine is conveniently admixed with the contents of electrolyte rfeed line 26 at a point not shown. Both f reshbrine and Ichlorine gas can be conveniently admitted directly into feed line 26 at the pump or just prior to the electrolyte 'reaching the pump, the turbulence produced at the pump being suicient to provide adequate mixing. It is yn'ece's'sary occasionally to add bro-mine or a bromide to the feed brine to make up for that bled on. NaBr is usually employed to bring the oxidizing normality up to at'lea'st 0.2 N.

AThe alkali or alkaline earth metal ions other than magnesium ions which have been introduced as the bromide in the start-up or make-up electrolyte employed, become largely depleted after the cell has been in use for a time, being gradually replaced by magnesium ions.

In practicing the invention employing a battery of the type shown in FIGURE 3, the procedure is little different The cells of the battery are placed in rm contact in electrical series. One method of attaining this is to employ a conducting cement between adjacent cells. A cement which can be employed for this purpose is one consisting of at least 50 percent battery-grade powdered graphite containing a bonding material; an example of such a cement is one consisting of 24 percent beeswax, 24 percent rosin, 2 percent gilsonite, and 50 percent of the graphite powder. The cells may also be firmly pressed together and sealed at the edges with a Vgood bonding cement, eg., Saran cement. Another way of making electrical contact is to employ copper plates as the contacting material between the cells, or to make connections between each of the cells by short copper wires or bus bars.

The following examples illustrate "modes of practicing the invention:

EXAMPLE 1 A cell of the type shown in FIGURES 1 and 2, having an anode and a cathode with areas of 60 square inches each exposed to the electrolyte in the cell, was assembled. The anode was 0.5 inch thick. The cathode was porous carbon having a porosity of 60 as determined by the porosity scale of the National Carbon Company. Cathode 12 was made secure in projection 16 of graphite plate 10 by means of graphite cement. The anode was a magnesiumbase alloy composed of 6.5 percenteAl, one percent Zu, 0.2 percent Mn, and the balance Mg. The anode was spaced 3/16 of an inch away from the cathode. The electrolyte was an aqueous sodium chloride solution of about 3 percent NaCl concentration into which was admixed vsuthcient sodium bromide to give, after introduction of chlorine, an oxidizing normality to the electrolyte of 0.6 N as determined by known methods, eg., by the indirect iodornetric method.

The sodium chloride electrolyte was saturated with chlorine gas by releasing the gas from a conveniently located drum, into the electrolyte as it passed through line 26 at the pump (not shown). r[he pH of the electrolyte was maintained between 2 and 3 by addition of The flow of electrolyte was maintained between H2804. 300 and 600 cc. per minute through the cell.

Conducting wires were attached to the terminals of the cathode and anode. A rheostat was connected to one of the wires for controlling the current ilow. An external circuit was then completed by connecting the wires to an ammeter, for measurement of current. A voltmeter was placed in parallel with the ammeter for measuring closed circuit voltage. Magnesium alloy wear was determined by gauging the thickness of the magnesum alloy anode and the magnesium consumed was determined by weighing the magnesium alloy anode before and after usage and subtracting to nd the difference. The actual amperage produced was determined by a series of readings of the ammeter. The readings were averaged and the ampere hours computed from the average for the magnesium consumed. The theoretical amperage was calculated according to Faradays law which shows the production 6 of about 1000 ampere Ihours `for each pound of magnesium consumed. The ampere eieienc'y was then calculated according to the mathematical expression:

Actual ampere hours produced Ampere elolency=1000 pounds of Mg consumed It is assumed that a pound of magnesium is roughly equivalent to one pound of anode.

The cell voltage was taken about every hour by means of a voltrneter and the average voltage calculated by dividing the sum of the voltmeter readings by the number of The cell employed in this `example was (a duplicate of that employed in Example l. Operating conditions were also generally the same except that the current density was reduced to below 0.2 ampere per square inch by in creasing the resistance by means of the rheostat. The results are set out in Table II:

Tab'le II Ampere eiiiciency percent- 43 Current density at anode ampere/sq. in. 0.19 Total ampere hours 1290 Average cell voltage volts 2.27 Weight of magnesium consumed pounds 3.0 Magnesium-alloy wear inch 0.63 Gxidizing normality of electrolyte 0.1 to 0.3 N

EXAMPLE 3 A ZOO-ampere bipolar cell, similar to that shown schematically in FIGURE 1, except for area, was constructed. The dimensions of the anode plate were 23% x 23%. There was a margin of Ss", around the anodle plate, which was covered by gasket 28, making the dimensions of that portion of the plate which was exposed to the electrolyte 22 x 22". The plate was composed of the same mag nesium-base alloy employed in Examples l Iand 2. It was s/s" thick and was spaced 1/8 from the porous carbon cathode at Athe start of the mn. The cell was sealed by a cement comprising a copolymer of vinyl chloride and vinylidene chloride. The terminals were connected through an external circuit as in Examples 1 and 2. FIhe brine contained from 10 to 14 percent MgCl2 and 64 grams of NaBr per liter. These amounts provided an oxidizing normality of 0.6 N. Approximately one liter of brine per minute was passed through the cell which resulted in a current ilow of about '200 ampeies through the external circuit.

The cell was operated for about seven hours each day for seven consecutive days. While Vin operation, amperes were usually drawn from the cel-l but for at least one hour each day, '200 amperes were drawn by adjustment of the rheostat. A summary of the results obtained are set out in Table III.

Table III Ampere eiiciency percent 41.7 Currentdensity at anode ampere/sq. in 0.206-.4l2

An examination of the cell in Example 3 after seven time.

days run, showed it to bein l very good condition. The porous carbon plate had not been attacked by any of the ingredients of the electrolyte; the magnesium alloy had been evenly worn to only about 1/16 thick over the exposed portion. A large portion of the remaining 24.9 percent anode weight was made up by the margin of the plate which was prevented from entering the action by gasket 28.

EXAMPLE 4 The multiple-cell unit shown schematically in FIGURE 3 of the drawing was constructed as follows: Five of the cells used in Example 3 were placed in firm contact so that the anode of one abutted against the cathode of an adjacent cell, leaving the anode of one end cell and the cathode of the other end cell as the terminals of the battery. The abutting cathodes and anodes were bonded together by means of the electrically conducting cement described hereinabove and clamped tightly by means of clamps 50.

The brine employed as the electrolyte in Example 3 with which chlorine gas was adrnixed was passed through the cells. The terminals of opposite polarity of each of the end cells were connected to a voltmeter and arnmeter through parallel circuits in a conventional manner for obtaining closed circuit readings; the readings were made periodically. A battery of five cells connected in electrical series was thereby put in operation. The results of six runs are set out in Table IV:

Table IV Oxidizing N of Ampere Electrolyte Run Amperes Volts Hours pH Feed Etlluent 114 8. so 220 0. 4o 0. 16 1. 9 90 8. 75 526 0. 41 0. 22 1. s s3 8. 51 389 0. 34 o. 17 2. 2 e6 s. 60 265 0. 3e 0. 12 1. 3 88 7.90 165 1.20 0.11 2.4 100 10. 60 0. 42 o. 23 0.7

The MgCl2 content of the eiuent electrolyte was determined during runs 2 and 4 and found to be 10.1 percent at the time taken for run 2 and 8.59 percent at the time taken for run 4. Under a 10D-ampere load, the average voltage produced per cell w-as 1.83 volts.

Experience with a similar multiple cell unit having copper bus bar connections between the cells instead of the graphite paste, shows that considerably higher ehiciencies are thereby obtained, approaching those of the single cell shown in Example 1.

By extrapolating the results of Example 4 and assun1- ing a current efficiency based on the magnesium alloy anode of 58 percent (obtained in Example 1), a 220- cell battery having an electrical potential of 40() volts (slightly over an average 1.8 volts per cell) capable of producing 500 amperes at a current density of .414 ampere per square inch and provided with anode plates of substantially the same material and thickness and spaced ls" from the cathode would require overall plate dimensions of 37 x 37" to give an active area exposed to the electrolyte of 1210 square inches.

When the cell of the invention is used in operating areas more or less remote from a servicing base or a maintenance unit, it is recommended that extra magtermined during runs 2 and 4 and found to be 10.1 perthe invention. To provide a continuous electrical source, two such 220-ce1l batteries are recommended. 7 sets of .magnesium alloy plates will supply 50,000 kilowatt hours when used consecutively in two 220-cell batteries of the type being described only one ofwhich is in use at one Two batteries .are recommended so that service need not be interrupted when worn plates are being replaced. l

The following ,summary shows the weight of each component or accessory and the ratio of this Weight to the kilowatt hours produced by two 220-cell units of the invention used alternately. The calculations are based upon au ampere efliciency of 58 percent and uponthe consumption of an average of percent of the weight of each anode before replacement.

In calculating the weights necessary to produce 50,000 kwh., an additional 6.4 percent was added thereto to provide for unanticipated loss, i.e., the weights were based on 53,200 kwh., but the weight ratios were based on an available output of 50,000 kwh. The ampere efliciency used in the calculations was 58 percent and the average percentage of the weight of each anode consumed before being replaced was 75 percent. To illustrate the method of calculating the weights necessary to produce 53,200 kwh., the weight of Mg plates for the consumable anodes is set out below:

-3l2(M)-99=133,000 ampere hours 133,000 1,000 .58 (efficiency) =229 pounds, the weight of Mg consumed 229 .75 (fraction of Mg anode used) the weight of Mg plates required for 1 cell 305 220 (No. of cells) =67,100 pounds,

weight of Mg required in 7 sets A number of advantages inure to the practice of the invention, among which are: adequate voltage and energy output for a wide number of activities associated with advanced field or undeveloped-area operations. Due to the high solubility of chlorine in the bromide-containing brine (in contrast eg., to the solubility of chlorine in the same brine but without the bromine component in an amount contemplated by the invention), the size of the chlorinating equipment is greatly reduced resulting in a low weight ratio of the equipment to the kilowatt hours produced. Due to the novel depolarization features, the cell operates at good etliciency until the magnesium-base alloy anode is substantially used up. The cell of the invention is generally adapted to mobile or floating units.

Having described the invention, what is claimed and desired to be protected by Letters Patent is:

1. A primary cell consisting of an anode composed of a metal selected from the class Aconsisting of magnesium, magnesium-base alloys, zinc, and zinc-base alloys and electrically separated inwardly therefrom a porous carbon cathode defining an electrolytic chamber therebetween, said anode and cathode each having a broad face disposed opposite each other at a distance of between 0.05 and 0.5 inch; a distributing chamber exterior of said cathode at the top thereof; conduit means for admission of an electrolyte into said distributing chamber;

= 305 pounds,

Van outlet at each end of said electrolytic chamber, and

2. A primary cell consisting of an anode composed of a metal electropositive to carbon and electrically separated a distance of between 0.05 and 0.5 inch therefrom a porous carbon cathode defining an elcctrolytic chamber therebetween; an electrolyte comprising a brine containing chlorine and bromine components suicient to maintain an oxidizing normality of at least 0.1 N and not over about 3.8 percent of a soluble magnesium component; a distributing chamber adjacent to the cathode outside the electrolytic chamber; conduit means for admission of electrolyte into said distributing chamber at the top thereof; an outlet at each end of said electrolytic chamber; and a pipe for conveying said electrolyte to a chlorinating means and back to said distributing charnber.

3. The cell of claim 2, wherein said metal electropositive to carbon is a magnesium-base alloy.

4. The cell of claim 3, wherein the magnesium-base alloy is composed of about 6.5 percent aluminum, 1.0 percent zinc, 0.2 percent manganese, and the balance essentially magnesium.

5. The method of producing electricity comprising chloxinating a `bromide-containing brine to give an oxidizing normality of at least 0.1 N, passing said brine thus chlorinated through a porous carbon plate into contact with a plate composed of a metal selected from the class consisting of magnesium, zinc, magnesium-base alloy, and zinc-base alloy which is connected to said carbon plate through an external solid conductor to produce thereby D.C., drawing olf at least a portion of said brine from contact with said magnesium alloy plate, rechlorinating the brine and passing the rechlorinated brine back `through said porous plate.

6. The method of producing electricity comprising `admiXing a soluble bromide in an aqueous solution to make a bromide-containing brine containing at least 8 grams of the bromine component per liter of electrolyte, chlorinating said bromide-containing brine to maintain an oxidizing normality of at least 0.1 N, passing said brine thus-chlorinated through a porous carbon plate into contact with a magnesium-base alloy plate which is connected to said carbon plate through an external circuit to produce thereby direct current, drawing 01T said brine from contact with said magnesium alloy plate, rechlorinating the drawn off brine, and recycling the rechlorinated brine through the porous plate.

7. The method of claim 6, wherein the soluble bromide selected from the class consisting of the bromides of alkali and alkaline earth metals in an amount sufficient to produce an oxidizing normality of between 0.2 and 0.6I N.

8. The method of claim 6, wherein sufficient chlorine is used to saturate the brine in chlorinating it.

9. The method of claim 4, wherein said anode is a magnesium-base :alloy `composed of about 6.5 percent aluminum, 1.0 percent zinc, 0.2 percent manganese, and the balance essentially magnesium.

References Cited in the tile of this patent UNITED STATES PATENTS 357,646 Upward et al Feb. 15, 1887 470,073 Ortelli Mar. 1, 1892 859,437 Divine et al. July 9, 1907 898,055 MacMillan Sept. 8, 1908 1,060,468 Little Apr. 29, 1913 1,119,024 Little Dec. 1, 1914 1,121,771 Sokal Dec. 2.2, 1914 1,258,266 Sokal Mar. 5, 1918 2,207,734 Heise et al July 16, 1940 2,273,795 Heise et al Feb. 17, 1942 2,612,532 Heise et al Sept. 30, 1952 UNTTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo MOTQUQYQ January 301I 1962 Robert Dvo Blue et @L It is hereby certified that error appears in the above numbered patent requiring correction and. that the said Letters Patent should read es line 66MI im@ vt-Jffrlzned during mme 2 and 4 and found to ,be T001 per-'m' reed neeum alloy platee tfiloeompaxoy the multiple cell unit of Signed andv sealed this 3rd day of July .1962,

(SEAL) Attest:

VERNEST w. SWIDER DAVID L- LADD ttesting Officer Commissioner of Patents 

1. A PRIMARY CELL CONSISTING OF AN ANODE COMPOSED OF A METAL SELECTED FROM THE CLASS CONSISTING OF MAGNESIUM MAGNESIUM-BASE ALLOYS ZINC AND ZINC-BASE ALLOYS AND ELECTRICALLY SEPARATED INWARDLY THEREFROM A POROUS CARBON CATHODE DEFINING AN ELECTROLYLIC CHAMBER THEREBETWEEN, SAID ANODE AND CATHODE EACH HAVING A BROAD FACE DISPOSED OPPOSITE EACH OTHER AT A DISTANCE OF BE- 